Solve for $t$ : $23 = t + 30$
Solution: Subtract $30$ from both sides: $ \begin{eqnarray} \\ \hphantom{23 {- 30}} &\hphantom{=}& \hphantom{t} \\ 23 &=& t + 30 \\ \\ {-30} && {-30} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 23 {- 30} &=& t \\ \end{eqnarray} $ Simplify. $ t = -7$